This invention relates to air compressors, and more particularly to an air compressor which has a compressor unit and a rotary drive unit for the compressor unit accommodated in a sound insulating box for the purpose of noise reduction and which is provided with a fan within the sound insulating box for efficiently cooling the compressor and drive units.
There are known in the art the so-called package type air compressors in which the compressor and drive units are housed in a sound insulating box for noise reduction. The air compressors of this type have an inherent drawback in that the inside of the sound insulating box is heated considerably due to insufficient ventilation necessitating to provide a fan for cooling the compressor and drive units. In this regard, as the compressor unit is subjected to the highest temperature because of the compression heat which is generated upon compression of the air, the usual practice has been to direct the currents of the cooling air from the fan toward the outer wall surfaces of the compressor unit as much as possible.
However, the conventional air compressors which are arranged to supply the cooling air for the compressor unit indirectly from outside are unable to cool directly the interior of the compressor unit, for example, the bearings in the crank case or the inner wall portions of the cylinder head where considerable heat is generated, thus failing to produce sufficient cooling effect. Similarly, it has also been difficult to cool the interior of the drive unit to a sufficient degree, including the coil and rotor of the drive unit. Therefore, the compressor and drive units are deteriorated acceleratedly, resulting in a shortened service life.
With the foregoing in view, the present invention has as its object the provision of an air compressor of low noise, which is arranged to effectively cool the component parts of the compressor.
It is another object of the present invention to provide an air compressor employing a duct for conducting cooling air currents from a fan directly into at least either a compressor unit or a dirve unit for effectively cooling the interior of same.
It is still another object of the present invention to provide an air compressor which is arranged to take in a large quantity of air from a fan, supplying cooling air currents in high velocity to a place in need of the cooling air without causing pressure drops or temperature increases to the air on the way.
It is a further object of the present invention to provide an air compressor in which cooling air currents are sent directly to a rotor and a coil portion of a stator of the drive unit, or a bearing and cylinder portion of the compressor unit which generate high heat, preventing early exudation of grease in the bearing and deterioration of the seal ring to prolong the service lives of the drive unit and the compressor unit.
According to the present invention, the foregoing objects are achieved by an air compressor which comprises: a compressor unit; a drive unit for driving the compressor unit; a sound insulating box having an air inlet and an outlet and encasing the compressor and drive units; a fan positioned in the sound insulating box on the side of the air inlet for suctioning air thereinto; a duct mounted in the sound insulating box and having one end thereof opened toward the discharge side of the fan and the other end opened into at least one of the compressor and drive units where cooling is needed.
According to one aspect of the present invention, a fan is eccentrically mounted in a cylindrical sound insulating box with the duct located in a position where the outer periphery of the fan most approaches the inner peripheral wall of the sound insulating box, thereby causing the air currents gushing from the fan to form vortex of cooling air within the sound insulating box and taking in the cooling air with a duct at a point where the velocity of cooling air becomes highest for supply to a part or parts to be cooled.
The above and other objects of the invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings which show by way of example preferred embodiments of the invention.